This invention relates to an improved method of preparing transition metal salts of organic carboxylic acids having improved stability and shelf life and wherein the transition metal is one capable of having a multiplicity of oxidation states. The invention also relates to the transition metals salt composition prepared in accordance with this procedure and to the use of said transition metal salts and a variety of applications including resins, inks, paints, lubricants and fuels.
Metal salt compositions, including transition metal salt compositions have been described in the prior art as being useful in a variety of applications including: siccatives for paints, varnishes and inks; stabilizers in diverse plastics; curing agents in polyesters; additives for grease and lubricating oils; and additives for fuels and fuel oils.
It is well known that metal soaps serve in a wide variety of specific industrial uses to catalyze the transformation of drying oils into solid condition by promoting the mechanism of oxidation, polymerization and association. Lead, cobalt, manganese and calcium soaps are among those commonly employed for this purpose.
Many types and mixtures of metal salts and soaps of natural or synthetic organic acids, particularly carboxylic acids, have been suggested and commercially offered for several decades. One of the advantages of metal salts and soaps of carboxylic acids is that they provide a source of metals in forms which are soluble in organic liquids, especially in various hydrocarbon oils and solvents, to form solutions having various desired properties and uses. The desire for economy in the production of such materials or for improved product quality has led to a number of variations and methods of producing the metal soap compounds. Moreover, as various organic carboxylic acids have become available in commercial quantities, either from new natural sources, or as synthetic acids or standardized synthetic acid mixtures, the possibility of using these acids to produce metallic salts or soaps has been motivated, for example, by a lower price; by a relative uniformity of the commercial acids; by better color; or at times the non-colored characteristics of the salt products; by higher solubility of the salt products and various solvents; or improved stability in storage of the metal compositions or of their solutions.
Methods of preparing hydrocarbon soluble salts of molybdenum and vanadium have been described in the literature. In U.S. Pat. No. 3,362,972, the process for preparing the salts of molybdenum and vanadium is described which comprises heating an oxalate compound of a metal of the group consisting of molybdenum at a valence of +6 and a vanadium at a valence of +5 with a hydrocarbon carboxylic acid of from 4 to 50 carbon atoms. The oxalate compound is prepared by heating oxalic acid with molybdenum or vanadium oxide in about equimolar amounts in the presence of water at a temperature of from about 100.degree.-150.degree. C. In U.S. Pat. No. 3,578,690, a procedure is described which does not require the use of oxalic acid. In the 690 patent, the process comprises the direct reaction of a molybdenum compound with a carboxylic acid at an elevated temperature while removing the water from the reaction mixture. A critical feature of this process is the removal of free water during the reaction, and generally, of about 100.degree.-300.degree. C. are utilized. In order temperatures to facilitate the removal of water, solvents such as lower alkyl benzenes and alkanes are included in the reaction mixture, and the water is removed azeotropically. Polish Pat. No. 89551 also describes a method of obtaining organic salts of molybdenum and vanadium. The method described in the Polish patent involves heating a mixture of molybdenum trioxide or vanadium pentoxide, an aliphatic alcohol containing from 2 to 8 carbon atoms, concentrated hydrochloric acid having a density of 1.179 at 20, a carboxylic acid in the form of a fatty or naphthenic acid, and alkyl benzene as a solvent. The mixture is heated at the boiling point of the mixture while continuously removing water from the mixture. After the reaction is completed, excess solvent is removed. It is reported that the mixture of aliphatic alcohol and hydrochloric acid functions as a reducing agent.
U.S. Pat. No. 3,076,830 describes and claims the preparation of water-soluble vanadium (IV) salts having as an anion, a complex of an oxo-vanadium group with an organic acid residue derived from an organic complexing acid such as glycollic, salicyclic and tartaric acids. The procedure comprises heating an aqueous medium containing a lower aliphatic carboxylic acid of 2 to 4 carbon atoms, a reducing compound such as hydrazine, and ammonium metavanadate until the evolution of nitrogen has essentially ceased, and thereafter adding a base consisting of hydroxides and carbonates of alkali metal and ammonium cations, and the organic complexing acid as defined above. The water-soluble salt then is isolated. The patentees teach (Col. 4, lines 51-54) that the vanadyl compounds prepared in the first step are useful also in the preparation of other vanadyl compounds.